<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="vue.js"></script>
</head>
<body>
<div id="root">
    <counter ref='one' @change="handleChange"></counter>
    <counter  ref='two'   @change="handleChange"></counter>
    <div >{{total}}</div>
</div>
<script>

    Vue.component('counter',{
        template:'<div  @click="handleClick">{{number}}</div>',
        data:function () {
            return {
                number:0
            }
        },
        methods:{
            handleClick:function () {
                this.number++
                this.$emit('change')
            }
        }
    })

    var vm = new Vue({
        el:'#root',
        data:{
          total:0
        },
        methods:{
            handleChange:function () {
                this.total = this.$refs.one.number +  this.$refs.two.number

            }
        }



    })














</script>
</body>
</html>